1. Technical Field
Embodiments of the invention relate to semiconductor systems.
2. Related Art
Each of semiconductor devices may include an input buffer circuit that receives external signals which are supplied from an external device or an external system. The input buffer circuit may also amplify the external signals to change levels of the external signals into appropriate levels (e.g., CMOS levels) which can be processed by internal circuits of the semiconductor device.
A differential amplifier circuit utilizing a current mirror scheme may be widely used as the input buffer circuit. The differential amplifier circuit may be an amplifier circuit whose output signal is directly proportional to the instantaneous differences between two input signals thereof. That is, the differential amplifier circuit may instantaneously sense and amplify a small voltage difference between the two input signals thereof to output the amplified signal. Thus, the differential amplifier circuit may be employed in fast semiconductor devices that operate at high frequency. In general, the two input signals of the differential amplifier circuit may be signals having two opposite polarities, or one of the two input signals of the differential amplifier circuit may correspond to a reference signal and the other one of the two input signals of the differential amplifier circuit may correspond to an input signal.